The invention provides digital dental devices using computer-aided system/computer-implemented methods. In particular, it is related to designing and manufacturing two or multiple layered blocks, disks or other forms for the fabrication of partial, full dentures or other prosthetic devices, specifically, milling partial, full dentures or other prosthetic devices and milling splints, orthodontic devices, retainers, partial or full denture bases using computer aided design and computer aided manufacturing (CAD/CAM) methods.
Dental devices, specifically for example, denture base and denture tooth should exhibit certain desirable physical characteristics to be suitable for use and offer desirable benefits to patients. They should be dimensional stable for effective functioning, sufficient strength to withstand masticating stresses and resistant to abrasion and chipping during use. They also should be durable and stable to solvents, foods, water, cold and hot and maintain esthetics without discoloration. In addition, they should be esthetics to mimic natural dentition and gum with esthetically acceptable color, i.e., close to that of natural dentition and gum. The denture base and denture tooth should not wear or deform out of occlusion, and denture base should be capable of being bonded firmly to artificial teeth. They should also be adjustable to ordinary means of physical shaping, grinding, and polishing. Denture base and denture tooth materials should be stable without discoloration and provide consistent handling properties during their shelf life. Denture fabricated from denture base and denture tooth materials should provide function, comfort and fit to the patients. It is desirable that denture base materials are compatible with hard and soft mucosal tissues. So it is desirable that denture base contains at least two different materials with different physical and mechanical properties. It is preferable that denture can be easily adjustable to provide better retention, better occlusal contact and better fit so as to provide better function, comfort and performance for patient. It is also preferable that denture can be locally adjustable while other parts remain unchanged.
Typically, denture bases are methacrylate-based acrylics, thermoplastic based or light curable resin based. Most common denture tooth materials are also methacrylate-based acrylics. In general, methacrylate-based acrylics denture bases and teeth are made out of dough from the blending of PMMA or modified PMMA polymer powders with MMA or modified MMA liquids. Denture teeth are commonly made in a tooth manufacturer. Dental lab typically uses denture teeth and denture base material from manufacturer to make denture for patient. The initial step(s) commonly used in the making a denture by making a final impression of a patient's mouth. A cast (or record base) is made of the final impression of a patient's mouth. Typically the cast is made of plaster. Then wax is shaped into the form of a denture base on the cast of the patient's mouth and artificial teeth are positioned into the denture base shaped wax. The denture base shaped wax with the artificial denture teeth is then positioned in an articulator. The artificial teeth in the denture base shaped wax are then articulated. The articulated denture base shaped wax with the artificial teeth is then positioned in a flask. The volume of the flask is filled with hardenable investment material, such as plaster. After the investment material hardens the wax is eliminated, for example by heating the flask in boiling water, leaving the artificial teeth supported by the investment material and a denture base shaped mold cavity within the investment material. After a thorough cleansing of the mold cavity a denture base material is introduced into the mold cavity. The denture base material then hardens to form a denture. The process to make a denture is long, time-consuming and labor intensive. In addition, this process produces a final denture by polymerization, where polymerization shrinkage and thermal shrinkage are introduced in the final formed denture, which adversely affect the fit of denture to the patient.
Preparation of full and partial dentures typically requires several dental office visits by each patient. The visits include labor intensive processes such as the construction of the base-plate and occlusion rims, wax try-in, invest the wax-up, wax removal and compression packing or pouring of denture base acrylic as described early. This traditional method typically resulted in a denture base containing homogeneous denture base material, which supported artificial denture teeth. A method of using light polymerizable wax like material (Eclipse system sold by Dentsply International) reduces the dental office and laboratory visits and the labor involved in making the denture, which provides a process for making a denture, comprising: articulating artificial teeth while supported by polymerizable material, whereby a denture comprising said artificial teeth is provided without forming a mold for making tooth setup volume of a denture base. The process is completed without forming wax and without applying inorganic plaster to the artificial teeth. Multiple layers of denture base materials are possible and are included in the denture base by this method. In addition, Even though lower polymerization shrinkage in Eclipse system resulted in better fitted denture, there is still polymerization shrinkage involved.
CAD/CAM systems have been using to make denture base in recent years. A disk shape homogeneous denture block is typically used for CAD/CAM milling to make denture base. These blocks are typically made of PMMA based polymer. Using acquired digital data, CAD/CAM machine mills a block to form desired denture base, where artificial denture teeth are subsequently placed into milled cavities and bonded to this denture base. Separately, some denture teeth are also milled by CAD/CAM and used to place into milled cavities and bonding to the milled denture base. This process produces the exact final denture base as designed to contact tissue side in oral cavity. Nevertheless, the fabricated denture may not fit in patient's mouth and teeth may not occlude correctly, additional adjustment or reline is needed that can be labor intensive and painful process. Denture may need to be remade that cost time, money and delay the patient care. Excessive grinding of teeth and denture base may be needed to achieve desired occlusion, which will result in the loss of esthetics of both fabricated denture base and artificial denture teeth and require additional finishing and polishing. It also faces the potential of grinding away more wear resistant enamel layers which commonly existed in some of artificial denture teeth and exposed the less wear resistant dentin layer. In order to avoid above issues, manufacturers and labs often make a try-in denture for the patient. After tried-in, adjusted and confirmed, and then duplicated the tried-in denture by milling or other fabrication methods, which adds additional steps back and requires additional office visits.
It is desirable the denture fabricated can be adjusted during final denture try-in to obtain desirable occlusion without the need of excessive of remaking, grinding, finishing and polishing. A denture fabricated where artificial denture teeth can be adjusted is highly desirable, which can avoid the need of additional tried-in step. It is also desirable the denture fabricated can be comfortable fit into oral cavity with rigid area to support artificial denture teeth and soft or relatively flexible contact surface to mucosal area for comfort and fit. Typically, denture bases are PMMA based acrylics. However, PMMA and MMA based denture bases have the disadvantage of being subject to brittle fracture due to the nature of PMMA. Rubber impact modified PMMA acrylics were used to improve their fracture toughness and impact strength. Full denture is typically formed from a rigid material since it is needed to support the artificial teeth chewing function without any movement during action. Flexible partial dentures, typically made of flexible thermoplastics, such as Nylon 12, acetal resin, etc. are being commonly used for patients, which provide comfort due to their compliance and flexibility. The use of clasps enables to stabilize the artificial denture teeth in place. The resilience and flexibility of these denture bases are limited due to the need to support artificial denture teeth. Significantly improved resiliency of tissue contact surface is desirable without compromising the artificial denture teeth stability during mastication. It is desirable to have a denture that provides a rigid ridge to support artificial denture teeth in position and resilient and flexible contact layer/area to patient's soft mucosal area for comfort and fit, which is more compatible to patient's oral cavity containing rigid ridge area and soft mucosal area. Common practice to improve the patient's comfort and fit is to reline a denture with a soft reline material, which requires additional labor intensive step. It is desirable to provide an integrated denture block or disk incorporating a soft layer or having two or more areas that offer different performances including a tooth adjustable area so as to be milled in a single step. It is desirable to provide an integrated denture block incorporating a soft liner/soft area into rigid denture base or having two or more areas that offer different performances so as to be milled in a single step. In addition, it is desirable that the contact surface of denture to mucosal area can be adjusted easily to get better fit. It is also desirable that the contact surface of denture to mucosal area can be adjusted and re-adjusted as needed, such as the need due to the ridge resorption over time. An adjustable polymer layer or a shape memory polymer is especially desirable to be used here. When digital intraoral scan is used for the fabrication of denture or denture base, a digital designed tissue side of denture may not perfectly fit to the oral cavity of the patient due to intraoral scanning involving soft tissues and an adjustable polymer layer or a shape memory polymer layer at tissue side allows the denture to be easily adjusted to the oral cavity of the patient to get the best fit and comfort. It is also desirable to have a denture, where limited tooth adjustment can be easily achieved. Denture base material around denture teeth can be easily adjusted at elevated temperature or other conditions is preferred. In addition, it is also desirable a shaded sealer/staining/paint may be used to achieve desirable esthetics/shades so that a multiple layered denture block or disk having tooth shaded layer(s) can be milled to form esthetic denture since it is highly possible that a denture milled from a multiple layered block or disk contains denture teeth having some denture base shade or denture base having some denture tooth shade. A computer or milling machine may detect shade difference or the need of sealer or painting through scanning device or code from predesigned block or disk, so as to mill extra thin layer of undesirable shaded material to accommodate the space for the application of needed shaded sealer.
Even though this invention referred mainly to denture, denture base and teeth, the disk or block of this invention is not limited to the milling of denture, denture teeth or denture base, they can be made into various shapes and shades and can be used to mill various dental devices, such as splints, nightguards, flexible partial dentures, flippers, orthodontic devices, aligners, retainers, frames, surgical guides, dental appliances, etc. The different layers of dental materials offer the dental devices with different performances, similar to denture and denture base with varied adjustability, physical properties and shape memory performance. Their shades can be formed from clear to highly pigmented shade. For example, a clear disk or block with multiple layers can be used to mill a multiple layered nightguard, where the hard and wear resistant top surface layer can effectively withstand wearing and grinding while a flexible or resilient side or the area below surface contact in nightguard can provide comfort, retention, adjustability and easy insertion and easy removal for the patient. Moreover, a surface adjustable layer can offer easy occlusion at chairside or in dental laboratory without the need to grind away materials to achieve desired occlusion. The denture base or denture tooth materials mentioned in this invention can be easily referred as dental materials, such as nightguard materials, retainer materials, or aligner materials, etc.
Grobbee (US patent application publication No. US20150245891 and US20150245892) claimed a method of manufacturing a layered denture in which the enamel layer is manufactured first from an enamel material blank, a dentin layer is formed and machined from the first denture material, and the denture base is manufactured last from the second denture material.
Giordano (U.S. Pat. No. 9,119,696) disclosed a dental blank has at least an inner zone of a first color and an outer zone of a second color, wherein the inner and outer zones are concentric. The dental blank has a geometric shape, wherein the inner zone is surrounded in its entirety by the outer zone such that only the outer zone is visible on all surfaces of the blank and the inner zone is not visible on any surface of the blank.
Howe (U.S. Pat. No. 6,641,938) claimed a method of milling a block of denture base material to form the first cavity to receive first denture tooth material and cured, milling the first denture tooth material to form the plurality of teeth. Final milling to form final denture comprised of a denture base and denture teeth.